Much research has been conducted concerning the phonological systems of young children developing normal speech production capabilities, but most studies have dealt with descriptions of 'higher-level,' linguistic aspects of their phonological systems rather than 'lower-level,' physical parameters. This latter perspective, however is important for obtaining a more broadly-based understanding of both normal and disordered phonological development. For example, it is known from acoustic measures that children's speech segments are longer in duration than those of adults; this is generally felt to be a result of children's less mature neuromotor capabilities. It is nuclear, however, whether such durational differences occur because children do not execute their articulatory gestures as rapidly as adults or whether they do not plan these articulatory gestures as efficiently as adults do. The primary method that will be employed for studying such issues will be the use of physiologic (strain gage) instrumentation to monitor lip and jaw displacements and movement velocities. Physiological measures of lip and jaw function relate closely to execution aspects of speech motor control and can be readily obtained. However, factors relating more to the planning component are more difficult to assess. Having subjects produce speech with bite-blocks inserted in the mouth or having them speak at various rates both seem to require them to operate in novel speaking modes. Results obtained from employing such approaches seem to provide significant information concerning the planning domain, since speakers are presumably required to re-organize the motor plans necessary for executing appropriate speech gestures. The purpose of this research will, thus, be to obtain an increased understanding of the development of speech motor control capabilities in young, normal children. The roles that both planning and execution factors have in children's speech production will be investigated. Such information will provide a more detailed understanding of normal speech motor control development, and it will also establish a basis for ultimately studying phonologically-disordered children and children with speech motor disorders. This clinical information has important implications for diagnosis and remediation of speech-related disorders.